The invention relates generally to tape recording and reproducing systems and in particular to systems for recording and reproducing information from a multichannel tape without interrupting the flow of information.
In multichannel tape recording and reproducing systems, information is generally recorded on or reproduced from one or more tape channels while the tape is run in a forward direction, the direction of tape motion is reversed and information is recorded or reproduced from different channels of the tape as the tape is run in the reverse direction. Reversing systems for automatically reversing the direction of tape motion have been developed. An example of one of these systems can be found in U.S. Pat. No. 2,213,631 issued to Heller et al., on Sept. 3, 1940. In this system, tape is driven first in one direction and then in the reverse direction with recording or reproducing of information occurring in each direction of tape travel on adjacent channels of the tape and reversal of direction occurring automatically as the end of the tape is approached. The reversal of direction however is not instantaneous but requires a finite transition time, including the time required for the tape to stop, to change direction of motion, and to return to proper operating speed in the new direction of motion.
There are many instances when it is necessary to record or reproduce information which continues for an indefinite period of time without interruption. Thus, in data acquisition systems, a data source furnishes data to a multichannel recording system for an uncertain time period which may exceed the storage capacity of one of the channels of the tape. Since it is undesirable to stop the flow of data to the tape system, it is necessary that the tape system be capable of recording the data on another channel of the tape without losing any of the information. Similarly, it is necessary to reproduce the information without losing any of the recorded information. The automatic reversing system described above will not meet this need since it requires a finite transition time to reverse the direction of travel during which portions of the continuous flow of information will be lost. To overcome this problem, relatively complex systems have been devised. One such system is disclosed in U.S. Pat. No. 3,445,832 issued to Leeke et al. on May 20, 1969. This relatively complex system utilizes two independent tape recording and reproducing systems and achieves uninterrupted information flow by recording the same information at the end of one tape in one system and the beginning of another tape in the second system. A control signal is recorded on special channels on both tapes concurrently with recording the information. During reproduction of the recorded information, the tape in the second tape system is started as the end of tape in the first tape system is approached. The control signals on both tapes are compared and when the tapes are running in phase synchronization, reproduction of information is switched to the second tape system without interrupting the flow of information. This system requires two complete tape systems and a relatively complex synchronization between the systems.